Getting Euler rotations for an object and exporting them
Should be as simple as:

from math import degrees

"{:f} {:f} {:f}".format(*map(degrees, obj.matrix_world.to_euler()))
# '-90.224203 -10.379210 -11.433244'


to_euler() converts a matrix to an Euler object, with order XYZ (regardless of what is set for rotation_mode). The angles are given in radians, but they can be simply converted to degrees using math.degrees().